I am with Snarlygribbly here. Installed Poser to the default locations (program files for the program and user/public folder for PoserPro runtime) and have had no issues at all on Windows 7 and I have UAC enabled. It is running Air and Flash64 without problems. I have my main runtime on another drive which I always attach to the new version of Poser.

I used to run Windows XP 64bit for a long time. You will have more compatibility issues with XP64 as with Windows 7 64bit. The compatibility with 32 bit programs and hardware is better and if needed you can use the included VM to install the 32bit version (which I never have needed to do).